The Structure of Diatoms. By Dr. J. H. L. Flogel 687 



Plate VIII. 

 Figs. 1-7. — Pinnularia mnjor. 

 k a, chamber, 

 me median \ ends of the same. 



k S, entrance to the chamber. 



m J, mid-rib. 



Fig. 1.— Transverse section through a valve touching the chamber openings 

 somewhere in the line at 4 in photograph 1 (or perhaps nearer the central 



Fig." 2.— Transverse section about the same place, line 5, in whii'h is contained 

 the vertical partition-wall between two chambers, the openings indistinct. 



Fig. 3.— Middle portion of a sim lar transverse section to illustrate a very 

 common appearance of the sloping away of the middle furrow, s, the closing 

 envelope which in many cases is torn during cutting, whereby balsam enters 

 into the cleft and produces the appearance of a continuous clelt through the 

 entire membrane. j i .i- o 



Fig. 4.— Transverse section touching the centre of the central nodule (line d 

 in photograph 1). , , , • • 



Fio- 5 —Part of a longitudinal section touching the chamber openings, i. e. 

 in the direction of the dotted line 1 in figs. I and 2, ur photograph 1. af 

 outer surface, and if inner surface of ihe cell-wall; k w, a vertical partition- 

 wall between two chambers. 



Fio- 6 —Portion of a longitudinal section along the side of the chamber 

 openiiigs, i.e. in the direction of the dotted line 2 in figs. 1 and 2 or photo- 

 graph 1. The membrane on the inner surface is much stronger than that on the 

 outer surface. • i m u ;i 



Fig. 7.— Diagrammatical figure of a collodion cast, a, a single i-sliaped 

 continuation in side view (as it becomes elucidated by the diff"ercnt focal 

 positions), b, a group of the same, in perspective as seen from above, z, the 

 smooth collodion surface, c, a piece of the serrated stripe whudi is formed 

 along the chamber openings, and on which the T continuations stand like a row 

 of trees, x, the collodion thread which was in the chamber, y, the spine of the 

 same, which inconsequence of the collodion contained in the opening contracts. 



Fig. 8. — Pinnularia QNaviculu) Crahro. 

 Transverse section from the middle of the valve, k a, chamber ; k o, opening 

 of the same. .-/ h, girdle-bands ; the outer has in all sections the position 

 figured ; the second valve is wanting. 



Figs. 9-12. — Navicula Lyra. 

 Three sections out of a series of 27 transverse sections through one valve. 

 Fig. 9.— jNIiddle secticm (No. 13) touching the central nodule m k, which 

 forms'^tt that point a very flat thickening, k a, chambers. 



Fig. 10.— Four se.'tions further on (No. 17). m r, mid-rib. I p, lyra plates. 

 k a, chambers. 



Fig. 1 1.— Section near the end of a valve (No. 1). 



Fig. 12.— Small portion of the surface-view of a valve of somewhat consider- 

 able size, corresiKJDiliiig to fig. 10. 



Plate IX. 

 Figs. 13-20. — SurircUa biscriata. 



q I, transverse ribs. 



7ft r, raid -rib. 



/ ', wing. 



r r, iiiurgiual tube in Ihe wing. 



